1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a vertical alignment (VA) mode type liquid crystal display device.
2. Description of the Related Art
Liquid crystal display devices are widely used as display devices for various kinds of equipment such as personal computers, OA equipments, and TV sets because the display devices have many advantages such as lightness, compactness and low power consumption. In recent years, the liquid crystal display device has also been used in mobile terminal equipments such as a mobile phone, a car navigation device and a game player.
In order to obtain a high quality display, further characteristics such as a wide viewing angle and a high contrast ratio are requested in the liquid crystal display device. Recently, a Multi-Domain type liquid crystal display device using Multi-Domain Vertical Alignment (MVA) mode in which a pixel includes a plurality of domains, has been used. In this type liquid crystal display device, the wide viewing angle is achieved by the plurality of domains. Further, a high contrast ratio which results in more complete black display is obtained because a retardation of the liquid crystal material becomes nearly zero. The liquid crystal molecules around an alignment film are aligned in a horizontal direction with respect to a substrate by adopting a homeotropic alignment treatment.
For example, Japanese laid open patent application No. 2008-197493 discloses a semi-transmissive type LCD using MVA mode by arranging slits or protrusions in a pixel electrode or a counter electrode. In this vertical alignment type LCD, variations in a cell gap holding a liquid crystal layer causes an alignment defect of liquid crystal molecules, which may result in a poor display, such as variation in the transmissivity, coloring in a case of a white display, or luminosity unevenness.